Please help me calibrate my 1993 flare side 5.0 E40D 2wd speedo . I went from 235/75/15 to 235/60/15 tires . I know this topic has been in the fourm before , but I have had no luck finding the information .Thanks Brandon

 

Found this on this post somewhere. I don't know if it works, I've never had to do it.

"Here Joe, Hope this helps ya out. i got this from another buddy, and I did it for mine and it worked out no problem.
Take care,
Rich

Here is the BEST way to calibrate your electronic speedometer.
Don’t try to calculate tire size, wheel diameter, revolutions per minute

etc. because this is all speculation and is subject to unknown error.
Simply drive a known distance from point A to point B and measure this
using your tripmeter. You can do this by using mile markers along the
freeway. The odometer and the speedometer are always related.
You change one and the other will change. Therefore, if you
drive 10 miles and your odometer says you only went 8 miles, you need
to decrease the conversion constant by 20 percent. The conversion
constant
is simply a numerical factor like 980 (approx. stock) that will appear
when your speedo
is in the calibration mode as explained below. When you INCREASE your
tire size you have
DECREASE this number to compensate. The constant can be decreased down
to 500 and
then will return to 1100. This sounds difficult but is much easier than
trying to calibrate
a gear driven speedo. NOTE: The module can only be reprogrammed SIX
TIMES.
Locate the dealer mode programming enable single-terminal connector.
The connector is located at the bottom of the instrument panel below the
center
of the glove box. On all vehicles, the dealer mode enable wire is
Circuit 567(LB/Y).
Insert a jumper wire or alligator clip in service wire and clip other
end to vehicle
ground with the key in the OFF position. Turn key to RUN while holding
down the
trip odometer RESET button on the speedometer. Release RESET button.
The Speedometer will prove out(sweep across dial and back).
The English/Metric and revision levels will be displayed. The last
number of
the display id the dealer mode lockout count. This count shows the
number
of allowable conversion constant changes remaining. When the count is
zero
(0), no additional changes can be made to this instrument cluster. If a

revision is required a service instrument cluster must be ordered. Press
and
release RESET button again and PSOM conversion constant without
the decimal point will be displayed followed by the word CAL. Press and
release the odometer SELECT button as many times as necessary to change
the conversion constant to the correct value.
Note: Pressing and releasing the RESET button to lock in the new
conversion constant reduces the number of times the PSOM can be
reprogrammed by one count. If you change your mind and want to go back
to
the old conversion constant, turn the key OFF BEFORE you lock in the
new
constant. When the new correct value is displayed in the odometer
window,
press and release the RESET button to lock in the new conversion
constant.
Turn the key OFF and disconnect the ground wire and check to see that
the
speedo works correctly."

 

That formula worked great for me on my 94 Bronco when I changed my tire size. It's a piece of cake to do it took me about 5min. Just make sure you make your do your odometer thing more than once and to check for accuracy.Also the longer the distance you go the less chance of error.(don't try to clock less than 10 miles)

 

does anyone happen to have the numbers that corellate to tire sizes for 1994? i have the complete directions on how to do the process, but don't have the numbers anymore.